1. Field of the Invention
The present invention relates to an adhesive composition for a semiconductor device.
2. Description of the Related Art
In the assembly of semiconductor devices, adhesion of a semiconductor die to a die pad of a lead frame or to a circuit board typically employs electrically conductive adhesives or thermally conductive adhesives. These adhesives are composed mainly of fillers, binder resins, hardeners, diluents, and additives. The binder resin per se is an insulator, but becomes thermally or electrically conductive if a filler with excellent thermal or electrical conductivity is dispersed therein.
For example, when silver (Ag) is used as a filler, an adhesive with excellent electrical conductivity is obtained. On the other hand, when silica (SiO2) or Teflon is used as a filler, an adhesive with low thermal conductivity is obtained.
The adhesive is typically heat-hardened at a given temperature for several minutes to several hours. When the adhesive is allowed to cool to room temperature after being solidified at a high temperature, thermal stress may take place due to the difference in the coefficient of thermal expansion between the semiconductor die and the die pad.
When the adhesive employs silver (Ag) as a filler, the thermal stress between the semiconductor die and the die pad is not sufficiently alleviated because a thermal expansion coefficient of silver is relatively large. As a consequence, this may undesirably result in the occurrence of delamination or cracking between the semiconductor die and the die pad.
On the other hand, when the adhesive is prepared using silica or Teflon as a filler, this may disadvantageously result in difficulty of rapid external dissipation of heat from the semiconductor die, due to significantly low thermal conductivity of the silica or Teflon as compared to silver. Consequently, electrical performance of the semiconductor device is also deteriorated.